1. Field of the Invention
This invention relates to methods for producing an optical element, optical elements producible by said methods, documents of value having such optical elements and a numbering embosser for use in an inventive method.
2. Description of the Background Art
Documents, certificates, bank notes, identity cards, plastic cards, etc., can be reproduced true-to-detail and colorfast using modern high-resolution color scanners and using color laser printers or thermal sublimation printers. The common availability of color copiers has also made it substantially easier to produce high-quality forgeries.
There is therefore a need to make documents, identity cards, bank notes, papers of value, plastic cards, etc., forgery-proof through additionally applied security features. Such security features can at least make it much more difficult and expensive to produce a high-quality forgery. Known security features are watermarks, silk threads, intertwined line structures, and the use of special paper. The application of metalized embossed holograms to bank notes, credit cards and Eurocheque cards has also become generally established. Due to the holographic effect, such embossed holograms can also be used for a special esthetic design of such documents or other objects.
Such embossed holograms are produced e.g. by embossing holographic image reliefs into an embossable film in bulk. An adhesive layer is applied to the embossed film. Further design is therefore no longer possible. With the adhesive layer the embossed film is applied e.g. as a security feature.
However, such simple embossed holograms likewise offer only limited protection from forgery. The increasing spread of corresponding technology already makes it possible to imitate such embossed holograms.
It would therefore be desirable if methods were available for producing optical elements whose forgery is further impeded and that permit simple individualization. It is the problem of the present invention to specify corresponding methods for producing optical elements, optical elements that are difficult to forge, documents of value having such optical elements and an embossing tool for use in a production method.